1. Field of the Invention
This invention relates to a rotary drum assembly for treating materials and more particularly to a rotary drum assembly having a pair of drum members connected for relative movement and maintained in sealing relation by a sealing assembly surrounding the end portions of the drum members.
2. Description of the Prior Art
In the process of making formcoke, as described in U.S. Pat. Nos. 3,073,351; 3,401,089 and 3,562,783, particulate bituminous coal and finely divided char (the solid carbonaceous residue of coal which has been distilled at a temperature of between 800.degree. and 1400.degree. F) are introduced into a rotary drum. Depending on the type of coal employed and the ratio of coal to char, pitch may also be added as a binder. The preheated coal and char supply substantially all of the sensible heat required to achieve the desired temperature for agglomerating the carbonaceous materials. The materials are intimately mixed by rotation of the drum. As the constituents are mixed, the coal particles are further heated to such an extent that partial distillation of the coal particles occurs, evolving tar and forming a loosely coherent plastic, sticky mass in the rotary drum. Rotation of the drum forms relatively fine plastic particles which grow in size as a result of the rolling or tumbling action of the particles on the upper surface of the plastic mass in the drum. The agglomerates grow in size until the binder evolved by the coal particles and the pitch binder, if employed, loses its plasticity. Thereafter, the agglomerates in the drum rigidify or harden to form uniformly sized agglomerates that are discharged from the outlet portion of the drum.
Rotary drums for agglomerating finely divided solid material disclosed in U.S. Pat. Nos. 2,778,056; 2,695,221 and 1,921,114; British patent specification No. 779,302 and Canadian Pat. No. 627,037 utilize a single drum in which the process steps of mixing, forming and hardening of the agglomerative materials to form the agglomerated product take place. It is essential during the process of mixing, forming and hardening the agglomerates that an inert atmosphere is maintained within the internal portions of the rotary drum. This inert atmosphere is maintained by the gases evolved from the agglomerative materials during the agglomeration process. To maintain the inert atmosphere, it is essential that a pressure exceeding atmospheric pressure (i.e. positive pressure) be maintained within the drum. Therefore, the end portions of the drum, as well as the access openings thereto, must be sealed in a substantially fluid-tight arrangement to prevent the escape of gas from the internal portion of the drum except the gas that is exhausted from the drum into the material. The seal also serves to maintain a preselected positive pressure therein.
A problem is encountered in maintaining a fluid-tight seal within the drum because of the fact that the temperature of the internal portion of the drum may vary considerably from the time that the constituents are first introduced into the drum and the final agglomerated product is discharged from the drum. Consequently, the drum experiences a substantial temperature change resulting in expansion and contraction of the drum. The longitudinal movement of the drum, due to expansion and contraction, presents a problem in maintaining a fluid-tight seal. Frequently, the seals are broken and gas escapes from the internal portion of the drum and consequently the desired pressure inside the drum cannot be maintained.
In treating materials there is need for a rotary drum assembly that is effectively sealed to maintain a preselected pressure within the drum and capable of compensating for expansion and contraction of the rotary drum assembly which occurs during the treating process.